Metal shield for tunnel-working



(No Model.)

T, DARK.

METAL SHIELD FOR TUNNEL WORKING. No. 286,789. Patented Oct. 16, 188.3.

UNITED STATES PATENT OFFICE.

rHonAs DARK, F BUFFALO, NEW YORK.

METAL SHIELD FOR TUNNEL-WORKING.

SPECIFICATION forming part of Letters Patent No. 286,789, dated October 16, 1883.

Application filed March 21, 1883. (No model.)

' zen of the United States of America, residing at Buffalo, in the county of .Erie and State of New York, have invented certain new anduseful Improvements in Metal Shields for Tunnel- WVorking, of which the following is a specification, reference being had therein to the accompanying drawings.

The object of this shield is to insure safety in excavating tunnels, headings, &c., in soft earth, sand, quicksand, 8rd, and give a better way of constructing the invert and arch of the brick masonry of such tunnels; also, to insure keeping the grade regular and the shape of the tunnel uniform throughout; and the invention consists in making the shield oval shaped in its circumference, of steel and cast-iron, in sections, bolted together, so that it can be taken apart as well as put together in the tunnel.

It further consists in other details of the construction of the said shield, as fully hereinafter explained.

In the drawings, Figure 1 is a vertical longitudinal section of the shield; Fig. 2,same view of shield in position in a tunnel; Fig. 3, a vertical cross-section through the whole shield, showing the connecting-flanges, &c., also the vertical upright snpporting post; Fig. 4, section. of the shield in line of a: m, Fig. 3; Fig. 5, cross-section of tunnel when finished as left by my shield.

A A represent plates or sections, usually six, of which the shield is constructed, of cast-iron, and fastened together by horizontal flanges running clear across each section and bolted by removable bolts, the flanges shown by black lines F F. That part of the shield projecting backward and marked Bis a hood,of steel and iron, and is fastened'to the sections A A.

D represents brackets, cast on the circular or circumferential flange a, and are used not only to strengthen the whole, but also to apply the screw-jacks c 0, (see Fig. 3,) to force the shield forward when required.

0 represents an upright iron T-post or column, bolted to the top and bottom of the shield.

not only to. strengthen the shield, but to be used, when required, to divide the head into two compartments, (1 d, for closing the whole or a part of the heading by placing boards 1) against the flanges of the T-post and flanges on the inside/of the shield when necessary to prevent the earth and sand caving in from the heading when excavating is not in progress, as partly shown in Fig. 4..

Back of the shield proper is a projecting hood, B, as before noted. This is of steel or boiler plates, made in sections, and fastened together the same as the shield-sections, and also to the shield. It rises about one foot above the exterior of the circular arch, as shown in Figs. 2-and 5, and thus forms a protection above the arch and side walls from points below the springing line of the arch J. This leaves an open space, H, between the top of the arch and the under side of the hood to allow for raising or lowering the masonry in the invert and to keep it to the proper grade in case the shield should be found at any time to be above or below the grade. It is also important, as it gives the mason or bricklayer room to properly key in the arch, and after to fill in the space H, between the arch and the soffit of the hood, with sand, &c., and prop erly pack the same before the shield is moved ahead. There is also a shorter hood, I, attached to the front of the shield, which projects a little beyond the invert, so as to prevent the roof of the tunnelfrom caving in.

The advantageof the use of this shield in dry sand or earth is that it can be moved ahead, so as to allow a length of five feet of invert and arch to be built complete and the backing filled in and packed before again moving the shield ahead.

In excavating a tunnel in quicksand the moving of the shield can be such as to lay the length of one brick all around in the invert to the springing of the arch, if required, and then move ahead the length of a brick, and so on, until the shield has been moved five feet, and then the arch can be completed, the same as in ordinary dry work, and the space H filled in and packed, as before explained.

G shows the open space left in the shield below the back of the hood.

There are various ways of constructing these shields; but by my device it is simplified, can beused more advantageously, and the masonry built more perfectly and left in proper shape without being disturbed when the shield is moved, as is the case with other shields.

The oval form of my shield is important in 2 nos/so 10 hood, substantially as set forth.

2. The combination of the sectional flanged metal shield A A F F, having the brackets D D, with the hood B, and front projection or hood, I, and the upright T-p0st 0, all arranged and operating substantially in the manner, I 5 and for the purpose specified.

In testimony whereof I afiix my signature, in presence of two witnesses, this 21st day of February, 1883.

THOMAS DARK.

Vitnesses:

J. R. DRAKE, T H. PARSONS. 

